You may want to check your battery if it is still the OEM before going great length trying to find the problem. With the deep freeze we had this winter, it may have killed your battery. I just replaced mine two months ago. It will jump start but it won't stay charged.

My advice is never jump start your ML,if the battery is dead replace it with new battery,if you have to jump start your ML remove key from ignition hook up jumping cable wait about 5-10 minutes before you start it.